1. Field of the Invention
The present invention relates to an ink jet printing apparatus, an ink jet printing method, data generating apparatus, computer program, and ink jet printing system by which a printing head that can eject an ink and a processing liquid is caused to scan a predetermined area on a printing medium a plurality of times to form an image by the ink on the printing medium and to cover the formed image by the processing liquid.
2. Description of the Related Art
In recent years, an ink jet printing apparatus has been widely used, with printed images having higher definition, for public display application and commercial display applications such as photographs, posters, and graphic prints. In the case of images formed for public display application and commercial display application, a requirement for high definition as well as a requirement for improving the image quality (e.g., uniform glossiness, bronze characteristic) and a requirement for improving the image toughness showing the strength and the long-term storage stability of the image. The bronze characteristic means a degree at which a color different from that of illumination light is reflected due to the bronze phenomenon when illumination light has mirror reflection (specular reflection) at an image surface. The bronze characteristic is known as being remarkable in a cyan ink in particular.
Coloring ink used in an ink jet printing apparatus is mainly classified to the dye-base one and the pigment-base one. Dye ink includes coloring dye dissolved in water or alcoholic medium in a molecular state and thus has a characteristic that dye ink is more transparent than pigment ink and provides superior color production. However, dye ink is disadvantageous in that early discoloring is caused due to ultraviolet light or active gas in air. On the other hand, pigment ink has a superior discoloring resistance in its long-term storage. In recent years, advanced manufacture techniques has allowed pigment ink to establish both of the long-term storage stability unique to pigment ink and superior color production equal to that of dye ink. Thus, more ink jet printing apparatuses use pigment ink mainly for demanding commercial printing applications such as photographs and posters where a printed image must be stored for a long term.
However, the application using pigment as described above in particular still has the conventional image quality-related problems such as the one where the glossiness of images tends to unequal and the one where the bronze phenomenon is caused as typical in pigment cyan ink. Another problem is that an increased number of display applications such as posters show a weaker image toughness that shows an image strength and a long-term storage stability compared to those of an offset-printed image for example.
The following section will exemplarily describe the problem of an abrasion resistance among the image toughness-related problems. The main problem is that an image printed on a glossy paper by pigment ink is easily damaged even in general handling operation steps such as the subsequent handling and display occasions.
FIG. 20A is a schematic view illustrating the cross section of an image formed by using a pigment ink on a printing medium having thereon an ink absorbing layer. The following section will described the reason why the image formed on a glossy paper by the pigment ink is easily damaged with reference to FIG. 20A.
A printing medium used for an ink jet printing apparatus is structured so that the surface of a base member (not shown) such as a paper or a film has thereon an ink absorbing layer 24 for the purpose of absorbing an ink. In order to reduce the oozing of the ink for example, the ink absorbing layer 24 includes a great amount of inorganic fine particles of silica or alumina for example that is highly-absorptive to ink solvent. A printing medium used for the printing of a photograph such as a glossy paper must have a flat and smooth surface and thus generally uses inorganic particles on the order of submicron. Thus, a gap among inorganic fine particles formed in the ink absorbing layer 24 is proportional to the particles diameter and thus is formed by a fine pore on the order of submicron.
On the other hand, in the pigment ink, coloring pigment particles of about 100 nanometer are dispersed. This prevents, when the coloring pigment particles has a diameter larger than that of the fine pores of the ink absorbing layer 24, the coloring pigment particles from entering the ink absorbing layer 24. In this case, the coloring pigment particles remain on the surface of the ink absorbing layer 24 as if they are blocked by a filter. In the case of a printing medium such as a glossy paper, the coloring pigment particles generally has a diameter larger than that of the fine pores of the ink absorbing layer 24. Thus, a pigment ink layer 25 is formed on the surface of the ink absorbing layer 24.
Due to the pigment ink layer 25 formed on the surface of the ink absorbing layer 24 as described above, the image surface is easily damaged when an external force is applied to the pigment ink layer 25. In some cases, the pigment ink layer 25 (image) may be peeled due to an external force. Due to the reason as described above, the image formed by the pigment ink has been considered as being frequently involved with abrasion resistance-related problems.
Japanese Patent Laid-Open No. 2000-153677 discloses a laminate film method to protect an image formed by a pigment ink by covering the printed face of the image by a cover film. Japanese Patent Laid-Open No. 2005-81754 discloses a liquid laminate method to cover the printed face of the image by transparent resin liquid. Japanese Patent Laid-Open No. 2003-170650 discloses a post-processing method to mix thermoplastic resin particles in the ink absorbing layer of a printing medium to print an image by a pigment ink to subsequently heat the printing medium to adhere a pigment ink layer to the ink absorbing layer.
In the case of the laminate film method, the abrasion resistance-related problem can be solved by the image surface covered by the resin film having a high film strength. However, the image surface covered by the film deteriorates the original texture of the printing medium such as a paper. The laminate processing also causes an increased cost because another apparatus different from a printing apparatus is required.
The liquid laminate method can carry out, just after the printing of the image, the liquid laminate processing in the same printing apparatus. However, in order to obtain the sufficient effect of the abrasion resistance, a film thickness of a few microns must be formed to deteriorate, as in the laminate film method, the original texture of the printing medium such as a paper. As disclosed in Japanese Patent Laid-Open No. 2005-81754, a further higher abrasion resistance is practically required when a thin film having a thickness equal to or lower than 1 micron is formed.
In the case of the post-processing method, types of printing media for which an improved abrasion resistance can be expected are limited and a heating processing step is required to cause the apparatus to have a larger size.
The problem of the abrasion resistance as described above can be very effectively solved by forming a transparent layer on the top layer of the pigment ink layer 25 on the glossy paper to reduce the dynamic friction coefficient of the image surface. To solve this, a configuration has been suggested for an ink jet printing apparatus in recent years to use a glossy paper including a transparent layer by formed a processing liquid including resin having an abrasion resistance function to print an image.
FIG. 20B is a schematic view illustrating the cross section of an image having thereon a transparent layer formed by a processing liquid. A transparent layer 26 of the processing liquid is formed on the outermost surface so as to cover the pigment ink layer 25. By the protection of the pigment ink layer 25, the transparent layer 26 allows the image surface from being peeled or damaged by an external force (e.g., contact with a nail), thus providing the image with an improved abrasion resistance.
Japanese Patent No. 3190535 discloses a method for using a printing head that can eject a processing liquid different from an ink in a multipath printing apparatus in which a plurality of scannings of a printing head that can eject the ink are performed to print an image on a predetermined area on a printing medium. For example, the processing liquid includes a cationic substance and forms a transparent ink layer different from an ink layer formed by an anionic dye ink. Specifically, after the application of the dye ink, the processing liquid is applied to form the transparent ink layer for improving the water resistance of the ink layer of the dye ink. Japanese Patent No. 3190535 also discloses a configuration, in the multipath printing apparatus, to apply the processing liquid in a final scanning of the printing head on the basis of processing liquid ejection data that is generated so as to apply the processing liquid to a position on the printing medium to which the ink is applied.
Covering the outermost surface of an image printed by an ink on a printing medium by a transparent layer is very effective to improve an image performance such as the abrasion resistance. However, in order to apply the processing liquid to the entire surface of an image printed by pigment inks of a plurality of colors, a relatively great amount of the processing liquid is required when compared to the amount of each color of the pigment ink. This has caused problems such as an ink tank for the processing liquid having a larger size and an increased running cost due to an increased consumption of the processing liquid for example.
As disclosed in Japanese Patent No. 3190535, when the processing liquid is applied only in the final scanning of the printing head, a great amount of the processing liquid is applied to the printing medium in the final scanning. Since a total amount of ink that can be absorbed by the printing medium at one time is limited, the processing liquid may be applied in the final scanning in an amount exceeding the limit. When the amount of the applied processing liquid exceeds the total amount of ink that can be absorbed by the printing medium at one time, the excessive ink may cause problems in the image performance such as a flooded ink phenomenon, bleeding, beading, defective drying, and a interference pattern phenomenon due to the transparent layer 26 finished to have a mirror surface.
When the multipath printing apparatus is structured so that the processing liquid is applied through the printing head for ejecting the processing liquid only in the final scanning, the printing head is driven in a concentrated manner in the final scanning. Specifically, among a plurality of ejection openings existing in the printing head, part of the ejection openings are used for the final scanning to eject the processing liquid in a concentrated manner. Thus, part of the plurality of ejection openings of the printing head for ejecting the processing liquid may have a deteriorated durability.
When the final scanning for applying the processing liquid is added separately from a scanning for printing an image, the printing apparatus must perform an increased number of scannings, thus deteriorating the printing speed (throughput) when compared with a case where no processing liquid is applied.